National Health and Nutritional Examination Survey data indicate that the prevalence of early childhood caries (ECC) in US children has increased significantly in the last decade, to 28% in 2 to 5 year-old children. ECC has a profound impact on a child's quality of life, is difficult to treat effectively, and has a distressing tendency to ecur following treatment. The oral biology leading to ECC is well-established, but knowledge of the biological mechanism has not led to very substantial progress in reducing ECC. In response to recent research evidence, there is a growing appreciation that assessments and interventions for ECC need to address social and behavioral mechanisms of risk; this is now a research priority (RFA-14-143). However, there remains considerable uncertainty about which social and behavioral factors may be most relevant, the strength of the evidence, and the mechanisms by which they operate. For example, socio-economic status (SES) is a reliable predictor of ECC, but indexes a broad array of plausible mechanisms and is not itself a practical intervention target. We adapt the findings from behavioral science which repeatedly show that low SES influences child health via proximal measures of child stress exposure, particularly caregiving and family stress. We propose a multi-disciplinary prospective longitudinal study of 206 children at-risk for ECC by virtue of low SES. Initially caries-free children aged 1-3 years will be followe over a 2-year period. At each of 5 dental visits we will conduct oral exams and assess social and behavioral risks, including caregiving and family stress. Cross-sectional and longitudinal analyses will consider the acceptability and construct validity and clinical relevance of caregivin and family stress measures for oral biology markers and ECC onset and course. Results from these analyses will identify key social and behavioral targets for the next stage of causal treatment research to improve oral health in young children. The specific aims of the project are to: 1) Identify social and behavioral risks relevant to ECC that are acceptable for a pediatric dentistry setting; 2) Assess construct validation for and clinical relevance of targeted social and behavioral risks for ECC; 3) Incorporate social and behavioral measures of risk in a broader prediction model of ECC. The proposed longitudinal study of ECC onset will guide the next stage of ECC interventions by developing social and behavioral risk measures that are suitable for pediatric dental setting and may index part of the causal pathway leading to ECC.